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EN
A solar cell is technically known as a photovoltaic device which converts light energy into an electric energy by the phenomenon called photovoltaic effect. Solar cells produce renewable energy and serve as a great substitute for conventional sources of energy such as petroleum, coal and natural gas. Solar cell is suitable for powering satellites due to its light weight and durability for several years, having ability to operate even in the vacuum space. It is also used in solar warm air electric power plants and every other PV powered devices ranging from heating systems, lighting, automobile to solar updraft towers and etc. It is of utmost demand to support research and development of renewable energy resources that would successfully power the world in the future without destroying the environment as the planet earth needs reduction in greenhouse gas emission. Immense progress has been observed over the years on several photovoltaic materials and devices based on conversion efficiencies.. This survey primarily focusses on different techniques and technologies analysed from the other cited references to enhance the working of a solar cell like selection of the most suitable material for each layer, various processing techniques and modifying the layer thickness of buffer. This review paper summarizes solar cell materials like Gallium Arsenide (GaAs), Silicon (Si), Cu(In,Ga)(S,Se2) (CIGS) and Cadmium Telluride (CdTe) that provide higher efficiencies when compared to other materials. In summation, it is understood that Gallium Arsenide solar cell provides highest efficiency when compared to Si, CIGS and CdTe based one junction solar cell. Factors such as, efficiency (ƞ), open circuit voltage (Voc), short circuit current density (Jsc) & fill factor (FF) have been analysed for the study of modeling, simulation and fabrication of solar cell. Detailed survey has been presented in this paper on different types of solar cells that would help the researchers to do more research on these solar cells.
PL
W artykule dokonao przeglądu i porównania różnych technologgi ogniw fotowoltaicznych. Przedstawiono ogniwa krzemowe, ogniwa bazujące na CdTe i CIGS oraz ogniwa bazujące na Gallium Arsenide (GaAs). W każdej grupie przedstawiono i porównano osiągane obecnie parametry I właściwości.
2
Content available remote Low-temperature growth of GaSb epilayers on GaAs (001) by molecular beam epitaxy
EN
Non-intentionally doped GaSb epilayers were grown by molecular beam epitaxy (MBE) on highly mismatched semi-insulating GaAs substrate (001) with 2 offcut towards (110). The effects of substrate temperature and the Sb/Ga flux ratio on the crystalline quality, surface morphology and electrical properties were investigated by Nomarski optical microscopy, X-ray diffraction (XRD) and Hall measurements, respectively. Besides, differential Hall was used to investigate the hole concentration behaviour along the GaSb epilayer. It is found that the crystal quality, electrical properties and surface morphology are markedly dependent on the growth temperature and the group V/III flux ratio. Under the optimized parameters, we demonstrate a low hole concentration at very low growth temperature. Unfortunately, the layers grown at low temperature are characterized by wide FWHM and low Hall mobility.
3
Content available remote Scanning capacitance microscopy characterization of AIIIBV epitaxial layers
EN
The applicability of scanning capacitance microscopy (SCM) technique for chosen electrical properties characterization of AIIIBV structures fabricated by Metalorganic Vapor Phase Epitaxy (MOVPE) was examined. The calibration curves for quantitative characterization of doping levels in GaAs layers were created. The AlGaN/GaN/Si heterostructures for high electron mobility transistor fabrication and InGaAs tunnel junction for tandem solar cell characterization were presented. The crucial factors of measurement conditions which could influence the obtained results were also discussed.
PL
W pracy przedstawiono wyniki modelowania lasera złączowego z pionową wnęką rezonansową o emisji powierzchniowej z warstwami oksydowanymi, emitującego falę o długości 980 nm. W ramach pracy przeprowadzono obliczenia cieplne, elektryczne i optyczne dla laserów posiadających dwie oksydacje, umieszczone w węzłach lub poza węzłami fali stojącej. Symulacje pokazały, że nawet niewielkie wysunięcie oksydacji z węzłów fali zmienia istotnie właściwości optyczne lasera.
EN
In this paper are presented results of numerical modeling of an oxide-confined vertical-cavity surface-emitting laser emitting at 980 nm. Simulations of thermal, electrical and optical phenomena were performed for a laser with the oxide layers at nodes of the standing wave and for a laser where the oxide layers were shifted by 20 nm from nodes. The simulations have shown that even such a small displacement change significantly some optical parameters of the laser.
5
Content available remote Point Defects in GaAs Photonic Crystals
EN
Applying plane wave expansion method to one dimensional multilayer system formed from alternating layers of GaAs and air, a defect mode was artificially introduced by removing a GaAs layer at the centre of a supercell and the band structures and mode field distributions were obtained. The defect mode normalized frequency was 0.28. The parameters for developing a Febry-Perot filter in the visible frequencies are given. The point defects in a two dimensional square lattice formed from GaAs rods of radius 0.16a in air was created by removing one GaAs rod at the centre of a supercell and also by increasing the centre GaAs rod radius to 0.5a. The removal of the rod folded the band structure 25 times creating a localized evanescent defect mode. The increment of the centre GaAs rod radius led to five defect bands inside the band gap with one degenerate state creating a monopole, two quadrupoles and two hexapoles. Evolution of the defect modes with the variation of the radius of GaAs rod is also presented.
PL
W artykule zaprezentowano przykłady rozwiązań wzmacniaczy mocy dla pasma C wykorzystywanych w systemach radiolokacyjnych PIT-RADWAR S.A. W pracy opisano wpływ konstrukcji szyków antenowych stosowanych w radarach na wymagania stawiane tego typu wzmacniaczom. Przedstawiono rozwiązania wzmacniaczy – realizowane w technologii GaAs i GaN. Rozważania teoretyczne poparto praktycznymi przykładami rozwiązań. Wskazano potrzeby i oczekiwania wobec możliwości produkcji tranzystorów i układów scalonych w technologii GaN przez rodzimy przemysł.
EN
Some examples of high power amplifier solutions for C-band radars, made by PIT-RADWAR S.A., are presented in the paper. The authors describe the influence of the antenna arrays structure, which are used in radars, on requirements on power amplifier parameters. Two types of power amplifier are presented in the paper – GaAs and GaN. Theoretical consideration are supported by presentation of some examples of practical PIT-RADWAR S.A. radar systems. At the end of the paper the authors present needs and expectations regarding the production of GaN transistors by polish industry.
7
Content available Simulation of two dimensional photonic band gaps
EN
The plane wave expansion method was implemented in modelling and simulating the band structures of two dimensional photonic crystals with square, triangular and honeycomb lattices with circular, square and hexagonal dielectric rods and air holes. Complete band gaps were obtained for square lattice of square GaAs rods and honeycomb lattice of circular and hexagonal GaAs rods as well as triangular lattice of circular and hexagonal air holes in GaAs whereas square lattice of square or circular air holes in a dielectric medium ε = 18 gave complete band gaps. The variation of these band gaps with dielectric contrast and filling factor gave the largest gaps for all configurations for a filling fraction around 0.1.The gap maps presented indicated that TM gaps are more favoured by dielectric rods while TE gaps are favoured by air holes. The geometrical gap maps operating at telecommunication wavelength λ = 1.55 m showed that a complete band gap can be achieved for triangular lattice with circular and hexagonal air holes in GaAs and for honeycomb lattice of circular GaAs rods.
PL
W artykule przedstawione zostały parametry fotodetektorów MSM wykonanych na warstwach czynnych GaAsN/GaAs i MQW InGaAsN/GaAs. Wszystkie warstwy czynne optycznie wykonane zostały w technologii epitaksji MOVPE. W warstwach GaAsN/GaAs struktura czynna GaAsN miała grubość 100...330 nm, a zawartość atomów azotu mieściła się w zakresie 0,85...2,2%. Struktury MQW InGaAsN/GaAs stanowiły trzy studnie InGa-AsN o grubości 15 nm i zawartości 11% indu rozdzielone barierami GaAs o grubości 30 nm. W pracy przedstawiono charakterystyki prądowo-napięciowe detektorów MSM bez i z oświetleniem, co pozwala określić podstawowe parametry wykonanych fotodetektorów. Z uzyskanych wyników widać bardzo wyraźny wpływ składu materiałowego wykonanych heterostruktur na fotoprąd i czułość wykonanych fotodetektorów MSM.
EN
In this paper the comparison of GaAsN/GaAs and InGaAsN/GaAs MSM photodetectors has been presented. All of the devices were made by MOVPE technology. The GaAsN/GaAs MSM devices were made on undoped GaAsN layers with concentration of nitrogen varied from 0.85...2.2%. The thickness of these layers was from 100...330 nm. The InGaAsN/GaAs active layer for MSM detectors consisted of triple InGaAsN MQW with 11% of indium in 15 nm thick QWs layers and 30 nm thick GaAs barrier layers. The dark and illuminated l-V characteristics of the designed devices were presented. The photoresponse characteristics have shown a strong influence of material composition on the MSM photocurrent for both GaAsN/GaAs and InGaAsN/GaAs heterostructures.
EN
One of the electrical characterization techniques of semiconductor structures with nanometer spatial resolution is scanning spreading resistance microscopy (SSRM). The applicability of SSRM technique for characterization of GaAs structures with n-type doping fabricated by metalorganic vapour phase epitaxy (MOVPE) was examined. The influence of scaling effect on the nanometer size AFM tip-semiconductor electrical characteristics was described. The results of characterization of device structure of magnetic field sensitive field effect transistor were presented.
EN
The process of via-holes fabrication in GaAs wafers was developed. Wet chemical etching both for substrate thinning and via-holes etching was employed. The solutions based on sulfuric and citric acid were tested in a wide range of compositions. The phenomena connected with the etching process like etching anisotropy and its influence on the shapes of etched holes were considered. At the end, possible applications of the new developed process were discussed.
PL
Opracowano proces wytwarzania otworów przelotowych w płytkach GaAs. Do pocieniania podłoża i do trawienia otworów zastosowano mokre trawienie chemiczne. Wykorzystano roztwory na bazie kwasu cytrynowego i siarkowego, które przetestowano w szerokim zakresie składów. Przeanalizowano zjawiska związane z procesem trawienia jak anizotropia trawienia i jej wpływ na kształty trawionych otworów. Przedyskutowano również możliwości zastosowań nowo opracowanego procesu.
PL
Przedmiotem badań w niniejszej pracy były głębokie pułapki w strukturach z GaAs:Si, które stanowiły odniesienie dla struktur z kropkami kwantowymi (quantum dots, QDs) z InAs/GaAs. Struktury te wykonano podobnie jak struktury z QDs, tj. epitaksją z wiązek molekularnych (molecular beam epitaxy, MBE) stosując technikę przerwy wzrostu w nadmiarze arsenu, jedynie wykluczając depozycję In. Pułapki charakteryzowano spektroskopią głębokich poziomów (deep level transient spectroscopy, DLTS), techniką pomiarów pojemności w funkcji napięcia polaryzacji, C-V, oraz wykorzystując obie te techniki w modzie profilowań wgłębnych. Profilowanie C-V włącza opis teoretyczny, który uwzględnia wyniki DLTS, tj. wysoką koncentrację defektów R4 i R5 i ich niejednorodny rozkładach przestrzenny. Umożliwił on interpretację tych zarówno już znanych, jak i nowych anomalii zaobserwowanych w takiej sytuacji w eksperymentalnych rozkładach koncentracji nośników. Zaproponowany model teoretyczny wraz z wynikami pomiarów w szerokim zakresie temperatury i ich prezentacją w postaci konturowych wykresów koncentracji nośników, Ncv, na płaszczyźnie we współrzędnych napięcia, VR i temperatury, T, (VR, T) stanowi alternatywne podejście w zakresie charakteryzacji defektów. Prezentowana metodologia profilowania C-V ma charakter ogólnego zastosowania i może być wykorzystana w diagnostyce zdefektowanych materiałów i struktur.
EN
Deep level transient spectroscopy, DLTS, and capacitance versus voltage measurements, C-V, as well as both techniques in their profiling modes, were used to study electron traps in MBE-grown GaAs structures. The structures were reference samples for devices containing InAs/GaAs quantum dots and were prepared by an identical technique, except for the introduction of the quantum dots. C-V profiling includes theoretical description and interpretation of new anomalies in the carriers concentration profiles found in the presence of the defects with high concentrations and inhomogeneous distributions. The theoretical model together with experimental results of free-carrier concentrations in a wide temperature range and their presentation in a contour representation on a (VR T)- plane is a novel approach for defect characterization. The methodology can be used for diagnostics and characterization of defected semiconductor materials and structures.
12
Content available remote SXDR64 – Multichannel low noise ASIC for CdTe and GaAs detectors
EN
A 64–channel ASIC called SXDR64 has been developed. The ASIC is aimed to work with DC coupled CdTe and GaAs detectors. Each channel of ASIC consists of charge sensitive amplifier, pole-zero cancellation circuit, 4th order shaper with programmable gain and peaking time from 115 ns to 380 ns, base-line restorer, two independent discriminators and two 20-bit counters. Simulated equivalent noise charge of the frontend electronics for 3 pF detector capacitance, detector leakage current of 500 pA and peaking time Tp = 380 ns is 123 electrons rms.
PL
SXDR64 jest 64-kanałowym układem scalonym przeznaczonym do odczytu sygnałów z detektorów CdTe oraz GaAs promieniowania X. Każdy kanał w układzie składa się ze wzmacniacza ładunkowego, układu kompensacji biegun-zero, układu kształtującego 4 stopnia, układu przywracania poziomu stałego, dwóch niezależnych dyskryminatorów oraz dwóch 20-bitowych liczników. Szumy oszacowane z symulacji wynoszą 123 el. rms, przy pojemności detektora 3p, prądzie upływu 0.5 nA.
EN
The analysis of results of experiment in the formation of periodic structures on GaAs surface by powerful laser radiation was conducted. The physic model of the process of structures formation was proposed. The numerical calculations of heating and melting processes of near-surface region was conducted.
PL
W pracy przeprowadzono analizę wyników eksperymentu obejmującego tworzenie struktur periodycznych na powierzchni GaAs za pomocą silnej radiacji laserowej. Zaproponowano fizyczny model procesu formowania struktur. Przedstawiono obliczenia numeryczne procesów ogrzewania i topienia obszarów przypowierzchniowych.
EN
The effects of HCl-based chemical and Ar+ sputter etching treatment on (100) GaAs surface properties with the aim to develop the procedure of surface preparation before metal deposition have been investigated. Variable angle spectroscopic ellipsometry, X-ray photoelectron spectroscopy, atomic force microscopy and photoluminescence have been used to study the surface characterization. We show that combining chemical etching in 5% HCl with Ar+ sputter etching gives the best results for surface cleaning prior to metal deposition. The application of this two-step treatment allows to obtain Ni/AuGe/Ni/Au ohmic contact with rc = 2×10–6 .omega.cm2 with excellent adhesion and long-term thermal stability.
EN
Processes of motion of threading dislocations associated with isovalent doping of epitaxial layers were considered. An exact solution was obtained for the gliding distance of dislocations under strains. It was shown that the effectiveness of doping for reducing the density of threading dislocations in an epitaxial layer depends on the product of the surface density of the dislocations in the substrate and the lateral size of the substrate. An analysis of the effectiveness of isovalent Bi doping and standard Pb doping in reducing the density of threading dislocations in GaAs epitaxial layers and the range of applicability has been presented.
PL
Zaprezentowano rezultaty badania wpływu dawki implantowanego indu na funkcję dielektryczną w implantowanych warstwach GaAs. Badania przeprowadzono metodą elipsometrii spektralnej.
EN
In this paper we present the results of spectroscopic ellipsometry study of changes in optical constants (refraction and extinction indices) of near-surface layers of GaAs caused by ion implantation. Parameters of models describing the samples have been compared with the results obtained for these materials by using the study with RBS-Channeling methods.
17
Content available remote Submicron suspended structures based on A(III)B(V) epitaxial layers
EN
A technological process has been described for fabrication of suspended structures on GaAs substrate with AlGaAs/GaAs epitaxial multi-layers deposited by the AP MOVPE method. The patterns of beams and bridges with various dimensions were made by the photolithography method. The structures were fabricated by wet chemical etching in two systems of solutions based on phosphoric or citric acid with hydrogen peroxide. The former one enabled etching through the deposited epitaxial layers down to the GaAs substrate. The latter one allowed a selective etching of GaAs over AlGaAs. In effect, a beam made of AlGaAs layer was released and formed the suspended structure. As an etching mask, AZ 1813 positive photoresist was used. A series of rectangular beams with various planar dimensions and submicrometer thicknesses was fabricated. The elaborated process may be used for fabrication of suspended structures for various applications.
PL
Opisano proces wytwarzania podwieszanych belek wykorzystujący głębokie trawienie monokrystalicznego GaAs. Przetestowano dwa systemy trawiące: na bazie kwasu fosforowego i cytrynowego. Najlepsze wyniki, zapewniające wytworzenie regularnych podwieszanych struktur uzyskano w roztworze kwasu cytrynowego w podwyższonej temperaturze przy użyciu maski z pozytywowego fotolakieru AZ 1813. Wytworzone struktury dają możliwość monolitycznej integracji z przyrządami elektronicznymi i optoelektronicznymi.
EN
The process of fabrication of suspended beams utilizing deep anisotropic etching of monocrystalline GaAs substrate has been described. Two etching formulas, based on citric and phosphoric acid have been tested. The best results, assuring successful fabrication of suspended structures were achieved in citric acid based solution at elevated temperature with AZ 1813 positive photoresist as etching mask. Obtained structures provide a great potential for monolithic integration with electronic or optical devices.
19
Content available remote Investigation of deep defects using generation-recombination noise
EN
Noise spectroscopy is an effective tool to characterize the quality of semiconductor bulk and surface and a figure of merit for device quality as a whole. In certain cases, low-frequency noise can be used for the evaluation of device reliability. Further, measurements of the noise characteristics of GaAs materials are a useful technique when it comes to studying deep defects exhibiting a thermally activated capture. In the paper we present the technique of noise spectroscopy and illustrate it with some applications. They include photocapacitive and noise measurements on a deep DX-like defect which gives rise to persistent photoconductivity in Mg-doped p-type GaN films. We also apply DLTS, photoconductivity and noise spectroscopy to characterize n-type bulk GaAs and an EL2-related metastable defect. The third example illustrates experimental results on the photoconductivity and noise of forward and reverse biased Al0.3Ga0.7N/GaN-based Schottky barriers. In the light of these results the nature and origin of the responsible centers are discussed.
EN
We report, for the first time to the best of our knowledge, on a passively Q-switched Nd:YVO4 laser with a GaAs absorber grown at low temperature (LT) by metal organic vapor phase expitaxy. Using the LT GaAs absorber as well as an output coupler, a passively Q-switched laser whose pulse duration is as short as 90 ns was obtained.
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